特大方量异形结构大体积混凝土冷却水管布置与参数研究

Cooling Water Pipes Distribution for Massive Concrete of Very Large Irregular Structure and Parametric Study

为避免特大方量异形结构大体积混凝土施工过程中产生温度裂缝,以沪通长江大桥桥塔下横梁为工程背景,采用MIDAS软件建立大型有限元温度场模型。针对下横梁大体积(11 600m^3)、高强度(C60)、结构不规则的特点,以内部最高温度及最大主拉应力为主控参数,优化冷却水管布置及相关参数选取。结果表明:冷却水管布置的间距越小、根数越多,下横梁混凝土降温越快,这会造成混凝土内部收缩过快,使得最大主拉应力变大;冷却水管通水温度越低、通水时间越长、通水流速越大,会导致与混凝土内部温差过大,增加收缩应力。实践证明,采用优化的方案后,各项温度参数均满足规范要求,有效地避免了结构产生有害的温度裂缝。

To prevent the occurrence of temperature-induced cracks in massive concrete of irregular structure during the construction process,the lower pylon cross beam of Hutong Changjiang River Bridge was taken as the study background.The MIDAS software was used to establish the temperature field model,in which the maximum internal temperature and the maximum tensile stress were applied as the major control parameters to optimize the distribution of cooling water pipes and the selection of related parameters,based on the characteristics of the lower pylon cross beam,like a large amount of concrete（11 600m^3）,high strength concrete（C60）and irregular shape.The results show that the spacing and number of the cooling water pipes have direct influence on the tensile stress,smaller spacing and more water pipes will cause rapid temperature falling in the lower cross beam,and consequently,the concrete inside will shrink too fast,leading to the increase of the maximum tensile stress.Whereas,the lower cooling water temperature,longer cooling time and fast water flowing speed will result in bigger inside and outside concrete temperature difference,and in turn,increase the shrinking stress.After the implementation of the optimized scheme,all the temperature parameters were proved meeting the code requirements,which helped effectively avoid the temperature cracks in the structure.